Permission to modify distribution group members

I have an SBS2011. I would like to give users rights to modify distribution group membership via Outlook. If I open Outlook as domain admin, I am able to add and remove members. If I open Outlook as a user (who is listed under "Managed by" for the distribution group along with the domain admin), I am not able to modify it. The domain admin is the owner of the group and the user is not.

How can I configure the distribution group settings or the user account settings so that a user or a security group of users can modify membership through Outlook without being the owner of the group?